Yes, I believe it is impossible because you have to collect all sheep, and the sheep from the corner are surrounded by 3 or 5 grasses, and under the grass is a flower requiring 3 more moves to get rid of. You also have to be lucky with the first moves otherwise the sheep from the middle top are not able to move. There's no…
As I said, this happens when I try to collect rewards, like the "rewards from the basket". It also happens when I select the store (the last item to the right at the bottom of the screen). There have been no ads for me since... ever.